Ultra-processed foods now form over half of the average diet in the UK, and for adolescents the figure climbs to roughly two-thirds of daily calories. These industrially manufactured products — packed with sugar, refined carbohydrates and flavour enhancers — are not merely empty calories that fail to satisfy hunger. Mounting evidence suggests they may be quietly rewiring the brain to demand more food even when the body has had enough.
How ultra-processed foods trick the brain
Dr Farhan Abdullah, a board-certified internal medicine physician and medical director of Magnolia Functional Wellness, explains that ultra-processed foods are primarily engineered for convenience and palatability. “Ultra-processed foods often lack nutrients but are high in sugar and calories, which can lead to over-eating,” he says. Their soft texture and high calorie density, however, are what make them particularly insidious, according to Dr Samuel Dicken, lead author of a landmark study from University College London and UCL Hospitals NHS Trust published in Nature Medicine.
“Their softer texture and higher calorie density make overconsumption more likely,” Dr Dicken notes. When food requires little chewing and breaks down quickly in the mouth, the brain receives weaker signals of fullness, allowing a person to eat far more before the body registers satiety. This mechanism appears to operate independently of nutritional content. The UCL trial found that participants eating minimally processed foods reported a two-fold greater improvement in overall craving control compared with those on an ultra-processed diet, and a four-fold improvement in controlling cravings for savoury items. The finding underscores how processing itself can alter the brain’s relationship with food.
Dr Abdullah recommends swapping out six common categories of ultra-processed items: speciality coffee drinks, packaged snack foods, chips, candy, pastries and breakfast cereals. Healthier alternatives include overnight oats or wholemeal toast with avocado for breakfast, lightly salted popcorn or vegetable crisps for snacks, and filo pastry for pies. The principle, he argues, is to choose foods in a state as close to their natural form as possible.
The UCL study: processing matters beyond nutrients
The UCL and UCLH trial enrolled 55 adults with an average body mass index of 32, placing them in the obese category. Each participant followed two eight-week diets in a crossover design, with a four-week washout period in between. Crucially, both diets were nutritionally matched according to the UK’s Eatwell Guide — they contained identical levels of fat, saturated fat, protein, carbohydrate, salt and fibre, and provided recommended intakes of fruit and vegetables. Participants were told to eat as much or as little as they wanted, with no calorie restrictions.
The results revealed a striking difference. On the minimally processed diet, participants lost 2.06 per cent of their body weight, compared with 1.05 per cent on the ultra-processed diet — effectively twice as much. This translated to an estimated daily calorie deficit of 290 kilocalories on the minimally processed regime versus 120 kilocalories on the ultra-processed one. The researchers calculated that if sustained over a year, the minimally processed diet could produce a 13 per cent weight reduction for men and 9 per cent for women, against 4–5 per cent for the ultra-processed diet. The greater weight loss came from reductions in fat mass and total body water, with no loss of muscle or fat-free mass, indicating a healthier body composition.
“This study highlights the importance of ultra-processing in driving health outcomes in addition to the role of nutrients like fat, salt and sugar,” said Professor Chris van Tulleken, co-author of the study and author of Ultra-Processed People. Because both diets were nutritionally identical, the degree of processing itself emerged as a significant factor in weight management. Dr Dicken added that while not all ultra-processed foods are “inherently unhealthy” based on their nutritional profile, their texture and palatability make overeating much more likely.
Independent experts have urged caution, noting methodological limitations and questioning whether the eight-week difference is clinically meaningful. They also point out that the ultra-processed foods used in the trial were higher in fibre than typical consumer diets, which may limit the generalisability of the findings. Nonetheless, the study establishes the first clear experimental link between processing levels and weight gain under real-world conditions.
Diets high in ultra-processed foods have been linked to a range of adverse health outcomes beyond obesity, including type 2 diabetes, cardiovascular disease, high blood pressure, depression, chronic kidney disease, colorectal cancer and increased risk of early death. These foods account for nearly 65 per cent of all free sugars consumed in the UK general population, and almost 80 per cent in children and adolescents.
Policy recommendations: shifting the focus from individual choice
The research team behind the UCL study has called for significant policy interventions. Professor van Tulleken argued that the global food system currently drives diet-related poor health and obesity “particularly because of the wide availability of cheap, unhealthy food”. He said: “It underlines the need to shift the policy focus away from individual responsibility and onto the environmental drivers of obesity, such as the influence of multinational food companies in shaping unhealthy food environments.”
Current UK government policies primarily target High Fat, Sugar and Salt (HFSS) foods, which overlap with many ultra-processed products. However, research suggests this approach misses a substantial portion of ultra-processed foods, particularly low-calorie soft drinks and white bread. Experts are calling for regulations that consider the degree of processing directly, rather than relying solely on nutrient profiling. The UK government reportedly dropped guidance urging retailers to offer discounts on minimally processed foods after lobbying from major ultra-processed food firms, underscoring the industry’s influence on policy.
Dr Dicken noted that the study aimed to fill gaps in knowledge about the role of food processing in relation to existing dietary guidance. The findings, he said, make a strong case for environmental interventions that reduce the availability and appeal of ultra-processed options, rather than placing the burden entirely on individuals to navigate a food environment engineered to encourage overconsumption.